Method of applying tubular rivets



Oct 1945. H. c. SUNDSTROM 2,387,692

METHOD OF APPLYING TUBULAR RIVETS Filed May 26, 1945 Patented Oct. 23, 1945 METHOD OF APPLYING TUBULAR RIVETS Harold C. Sundstrom, Chicago, 111.

Application May 26, 1943, Serial No. 488,553

1 Claim. This invention relates to rivets andmore particularly to an improved tubular rivet and a novel method of applying rivets of that general character to articles desired to be joined together.

The present invention is particularly adapted to overcome the deficiencies of the various forms of known rivets and the existing unsatisfactory methods of applying the same which have resulted in the formation of imperfect unions betweenriveted articles. Heretofore, when it was desired to fasten together two articles by the use of a hollow, tubular rivet, the rivet was first inserted in the preformed aligned openings of the articles after which pressure was brought against the ends of the rivet by various means so as to upset at least one end thereof. As a result the articles were confined between the upset portion and the other retaining end of the rivet. Although a union between the articles was effected to some degree in that the two articles were held together in such a manner that they could not be entirely separated one from the other, nevertheless the effected union was imperfect and not a tight positive one whereby the articles would be incapable of relative movement in any and all directions. In such unsatisfactory unions, the articles were still capable of a slight amount of relative movement in various directions and particularly relative twisting or rotative movement with respect to each other about the rivet as a pivot point. These loose unions were especially undesirable where the articles were subjected to substantial vibration, twisting stresses and other strains during normal use or operation of the structure of which the articles were parts. Also it was found that upon upsetting hollow rivets having a closed head end portion, the central portion of the head end collapsed or became distorted or depressed with the result that an irregular head having an irregular retaining flange was produced which collected dirt, increased wind resistance, and had other disadvanta es.

The same general problem and failure to achieve unions between articles that were tight, positive and satisfactory in all respects has existed also in the use of solid rivets. It has been recognized that one of the principal reasons for such imperfect and loose rivet unions is the fact that the shank of the rivet, which normally is of such dimension as to permit its ready insertion into the preformed openings of the article to be riveted together, fails to tightly engage the vertical side walls of the preformed openings upon the rivets being upset by the old well-known methods to fastening position. The slight clearancespace which facilitates ready insertion of the rivet into the preformed openings is not taken up by the rivet when it is upset and, consequently, slight relative movement between the articles is permitted.

To overcome the foregoing dimculties and deficiencies, various efforts have been made by skilled workers in the art. These efforts, however, prior to my invention, had been proven failures or had been rewarded with only partial success, leaving the problem as yet unsolved. One

attempted solution has been by the well-known method in use today whichv comprises first cooling or reducing the rivet to a very low degree of temperature so as to shrink its overalldimensions and then applying 'the rivet when still cold into the preformed openings of the articles to be riveted, the openings being slightly larger than the reduced dimension of the cold rivet. The underlying theory of this cold method isthat the rivet upon returning to its normal temperature would expand to its normal size and, thereby, into a snug, tight engagement with the sides of the preformed openings. However, this cold method has not been found satisfactory since the shrinkage of the rivets by cooling is relatively inconsequential and insufficient to achieve the desired results, and the resulting expansion of the rivet in returning to normal temperature produces only a limited but ineffectual tightening of the frictional engagement between the rivet shank andthe side walls of the openings.

Another attempt, for example, to secure a satisfactory tight engagement was the provision of a rivet of larger dimension than the preformed openings of the articles, which rivet necessarily had .to be forced through the openings preparatory to upsetting its head. This method was also a substantial failure in that the rivet was often damaged upon its insertion in the smaller holes and the articles being riveted were often distorted.

Other attempted methods, although achieving a limited success, nevertheless have been found to be expensive, complicated and hence commercially impractical.

It is, therefore, an object of my invention to provide an improved rivet comprising a tubular portion and a substantially incompressible filler within said tubular portion that is fiowable under pressure to effect expansion of the rivet into positive tight engagement with the side walls of the openings of the articles being riveted together.

Another object of-my inventionis toprovide an-improved' rivet having a: tubular portion. a-

closed head at one end of said portion and a pro-- formed flange at its other end and a filler within the tubular portion comprising a relatively incompressible material thatis flowable under pressure.

A further object is to provide an improved method of applying a hollow tubular rivet to fastening positionin two or more articles to be riveted togethe which comprises expanding. the rivet upon the application-of upsetting pressureinto tight positive engagement with the side walls of the openings of the articles through which the rivet extends.

A still further object of my invention is to provide an improved method of applying'a hollow tubular rivet to fastening position in two or more articles to be joined to ether-"which comprises substant ally filling'the rivet with'a relat vely incompressible filler thatnis flowable under pressure. inserting thefilled rivet throu h the art cles to be riveted. applyingrelative pressure -to both ends of sa d rivet to upset one or bo h of. said ends into fastening position and confining sa d filler within thetubular portion during the appl cation of said upsetting pressure. so as to ex and the tubular portion of the rivet into tight positive engagement with theside walls of the open n s of the articles through which the rivet extends. Still another object is to provide an inexpensive seamless, tubular sheet metal rivet that may b quickly and easily applied at normaltemperatures to articles to be joinedtogether by the use of any of the present well-known riveting or upsetting means so that a tight positive engagement between the rivet andthe side walls of the openings of the articles being riveted may be elTected.

Another object is to provide an improved meth- 0d of applying a hollow tubular rivet having a tubular portion, a closed head at one end of said portion and a preformed flange at its openend.

to articles to beriveted together,. which comprises first filling the rivet with a relatively incompressible filler, such as*soap,grease or other material of similar consistency that is flowable under pressure, inserting the filled rivet through the preformed openings of articles to be riveted together. then placing theflanged end of the rivet against a supporting surface to close the open end thereof and confine the filler Within the rivet, then applying a compressive force vertically of saidrivet to upset the closed end thereof and to expand the tubular portion outwardly into a tight positive engagement with the side walls of the cpenings of said .articles, and finally, if desired, removing the filler material from the rivet.

Other and further objects and advantages will become apparent asthis description progresses, reference being had to the accompanying drawing, in which:

Figure 1 is a vertical sectional view of my improved hollow tubular rivet in unfilled condition:

Fig. 2 is a substantially diagrammatic and vertical cross-sectional view illustrating two of my improved rivets being carried by a belt during the operation of loading the rivet with the flowable filler;

Fig. 3 is a vertical sectional view of my improved rivet containing the flowable use: I

Fig. v4 is a vertical sectional view of my improved rivet inserted through the preformed openings of two sheets of material to be united;

filler and ready for rivet in'posi-tionbetwecn pressure applyingmeans;

may be stamped from'thinsheets offany one of many well-known kinds of metalsuch as aluminum, steel. copper; tin, magnesium and other metals'and alloys suitable for riveting-purposes. The rivet is seamless and has relatively. thin walls. It

is substantially circular and comprises a vertical" tubular portion If], a closed endor head portion H. at its upper end-andan outwardly extending annular flange [2 at its lower open end. The walls of the rivet head H where they join with the verticalportion in are rounded as indicated by the numeral l3. The rivet is of such construction that its upper portion including the head II with its rounded portion l3 and the upper end of. thetubular portion I0 may be collapsed or upset in the manner to be described hereinafter and as shown in Fig. 6. The walls of the tubular portion ID are also of such construction that they may be expanded outwardly by the application of expanding pressures against the. inner surfaces thereof by a manner also to be described more fully hereinafter;

After the rivet has been stamped in the form and construction shown in Fig; land described above, it is then substantially filled with a relatvely incompressible filler material, such. as soap, grease, any jelly-like or plastic substance of similar consistency, or any other material or substance that is readily flowable under pressure. Any one of a great number of substances may be suitable as the filler. be of such a consistency and character that it may be readily placed within the hollow cavity [4 of the rivet and retained therein without the pro-v vision of additional means during handling or shipment of the rivet even though. the rivet be manually or automatically by machine in the.

event mass production of the rivet is desired.

One form of mass production or filling ofthe rivet with the flowable material is illustratedsomewhat diagrammatically in Fig. 2 of the drawing wherein the rivets l6 and 11 are carried by an intermittently movable belt I8 in inverted position, as compared to the position of the rivet shown in- Fig. 1, with their open ends up and extending downwardly through openings IS in the belt l8 The rivets l6 and I! are supported from the belt l8 by their annular flanges 12. The belt is operated by a suitable mechanism (not shown) for intermittent movement and passes under a feed mechanism 20 from which a suitable filler material I5 in a hot liquid state may be intermittently fed in a predetermined quantity into each rivet as the rivet is momentarily stopped in feeding position directly below the feeding mechanism 20. As shown in Fig. 2, the rivet l1, supported on the belt l8 which moves toward the right, has already been filled with the filler material which has already begun to cool, while the rivet IS in the left hand side of Fig. 2 is under the feed mechanism 20 and is in the process of being filled with the filler in its hot liquid state.

The belt i 8 may be of such a size and length that the filled rivets l6 and IT may be carried a Preferably, the filler material should suflicient distance thereby to enable the filler material to cool sufiiciently soas to assume its jelly-like or no mal semisolid consistency. The cooling of 'the filler may be hastened by passing the belt l8 andthe rivets l6 and I1 through a special cooling zone (not shownl. When the filler (5 has cooled to its normal semi-solid consistency at which it, is still flowable under pressure, the rivets may be removed from the belt by "appropriatemeans (not shown) and packed immediately for shipment, since at this time the rivets may be turned over to theopen side down position shown in Fig. 3, or handled in any manner, Without the provision of additional means to prevent the filler Hi from falling out or becoming dislodged from the cavity l4. My improved rivet, therefore, lends itself readily to commercial production, sale and shipment to the users thereof.

After the .rivet has been filled with the flowable filler l5, it may then be inserted upwardly through aligned. preformed openings 22 and 23 of two members 24 and 25 which are desired to be riveted together. It is to be noted. however, that in practicing my improved method the flowable filler may be placed within the cavity 14 of the rivet either before or after the rivet has been inserted through the preformed openin s 22 and 23. The outside diameter of the tubular portion ID of the rivet is less than the diameters of the openings 22 and 23 in order that the rivet may be readily inserted in the openings 22 and 23 without damage to the rivet itself or to the members 24 and 25. is indicated clearly in Figs. 4 and 5 by the small space that exists between the rivet and the vertical walls of the openings 22 and 23. It was the existence of this small space after the rivet had been upset to fastening position that partially cau ed the undesirable loose unions and ermitted relative movement between two riveted articles where rivets of the old ty es were a plied by the old well-known methods. As will be described hereinafter, th s space is entirely eliminated with the use of the present rivet applied by the present improved method with the result that a ti ht positive en agemept is achieved between the tubular ortion l and the vertical I walls of t e openin s 22 and 23.

After the rivet has been inserted in the openings 22 and 23, it mav then be placed. as a further step in my improved process of riveting and as illustrated in Fig. 5. a ainst a substantially fiat upper surface of a relatively immovable support member 21 with the, under surfaces of the rivet flan e l2 in en a ement therewith. During the upsetting operation the su port member 21 serves to support the rivet a ainst withdrawal from the openings 22 and 23 and to close the open end of the rivet to prevent leakage of the filler l therefrom under pressure.

In Fig. 6 of the drawing, the next step of my improved process is shown. A movable upsetting means. 28. shown dia rammatically and in raised or removed position in Fig. 5 and which may take the form of any of the well-known rivet upsetting means. has been depressed with relatively great pressure a ainst the head portion H of the rivet so as to colla se and upset the head portion and form a substantially flat annular retaining head This difference in diameters,

flange 29. U on collapse of the upper portion expanded outwardly into a very tight and positive engagement with-the vertical side walls of the openings 22 and 23. By this expansion the space resulting from the differences in diameter between the tubular portion III of the rivet and the openings 22 and 23 of the members 24 and 25 is completely eliminated as are all the disadvantages resulting from its existence.

In addition toserving as a pressure transmitting medium for expanding the tubular portion ID, the flowable filler 15 also enables the rivet head I I to be turned over or be upset properly in a fiat, uniform manner. The upset annular retaining flange 29 formed by the present method is of substantially uniform radial dimension throughout its entire circumferential extent and the entire head is fiat, unwrinkled and undistorted. The flowable filler l5 successfully resists collapse, distortion or depression of the head I l at its center where such tendency is greatest during the upsetting operation. The elimination of such depression and distortion of the head prevents the collection of dirt, decreases wind resistance, and prevents the creation of air eddies, which are considerations of prime importance in. aircraft moval of the filler I5 is particularly desirable where reduction of weight is a consideration. This removal may be accomplished by hand with the use of simple tools or by the application of heat, if the filler is one which may be liquidated by heat. as shown somewhat diagrammatically in Fig. '7, wherein the rivet in upset position is passed over a source of heat 30, or through a heating zone, in order to reduce the filler 15 to a liquid state and permit it to run out of the rivet cavity M.

In many instances, where weight of the structure being riveted is not an important factor. the filler may be permitted to remain in the rivet. In other instances where use of the riveted structure requires that the cavities I! be filled so as to present a relatively smooth surface on the underside of the rivet, a'plastic material that is flowable under pressure and which will harden or set at normal room temperatures or by the application of heat may be employed with satisfactory results.

It will be understood that my invention is not limited to the precise details of construction and operation described with reference to the drawing, and that modifications of form of the rivet may be made, various types of filler materials that are relatively incompressible and flowable under pressure may be used, and various means of performing the steps of the process may be employed, without departing from the spirit and scope of my invention as defined in the appended claim.

I claim:

The process of applying in fastening position to parts to be fastened together a hollow rivet comprising a tubular body having an opening at one end and thin collapsible side walls at its other end portion projecting beyond the parts to be fastened and a closed head integrally formed with said thin side walls, which process comprises the steps of substantially filling the interior space of the hollow rivet with asubstantially incompressible filler that is fiowable under pressure so that the filler is in engagement with the interior faces of the tubular body and the thin side walls and head thereof, closing the open end of the rivet to prevent escape of the filler under pressure. applying axial pressure against the outer surface of the closed head, transmitting said pressure against the inner i aces of the tubular shank and the thin walled portion thereof by means of said filler to expand said tubular shank outwardly into engagement with the parts being fastened together and to effect collapse of the thin-walled shank portion radially outwardly as the head moves in an axial direction under said axial pressure. and preventing distortion and collapse of said head in an axially inward direction by means of said filler upon application of said axial pressure to the outer surface of said head, whereby a substantially smooth-surfaced retaining element of greater diameter than the tubular shank is formed in fastening engagement with one of the parts being fastened.

HAROLD C. SUNDS'I'ROM. 

